Extension grate for multiple retort underfeed stokers



May 2, l939- T. G. w. WATSON ET AL 2,156,546

EXTENSION GRATE FOR MLTIPLE RETORT UNDERFEED STOKERS Filed Oct. 2l, 1936 2 Sheets-Sheet l MAL Filed Oct. 2l, 1936 T. G. w. WATSON Er Al.

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EXTENSION GRATE FOR MULTIPLE RETORT UNDERFEED STOKERS May 2, i939.

Patented May 2, 1939 Unirse stares ?ATENT FFCE EXTENSION GRATE FOR MULTIPLE RETORT UNDERFEED STOKERS Thomas George William Watson and John.

Application October 21, 1936, Serial No. 106,728 In Great Britain November 13, 1935 5 Claims.

This invention relates to extension grates for multiple retort underfeed stokers and has for its object to provide a more eicient and simplified extension grate structure than those hitherto in use.

The present invention mainly consists in an extension grate for multiple retort underfeed stokers comprising a series of stationary and moving Tb.; bars alternately arranged, the said moving bars imparting an upward movement to the fuel and ash thereabove.

An important feature of the operation of mutiple retort underfeed stokers is the underfeeding of the coal to the fire in such a manner that the ash from the consumed coal is continuously lifted and carried onwards in the surface layer of the fuel in an increasing concentration towards the rear end of the grate.

'I'he underfeeding of the fuel down the tuyre section of the grate surface is dependent on the resistance at the rear end of the stok-er and to obtain uniformity of underfeed it is necessary to maintain a uniform resistance across the entire Width of the stoker. It has hitherto been the custom to use the ash at the top of the ash pit as a resistance and the obvious disadvantage of this is that the resistance varies due to theeiect of grinding on the level of the ash pit, which variation of resistance inevitably militates against uniformity of underfeeding.

As previously stated, the ash is carried down the tuyre section of the grate surface by a continuous lifting and onward movement of the underfed fuel.

The extension grate which has hitherto been in use had only an onwardly moving effect on the fuel and as a consequence of this, it allowed the molten ash to sink through the fuel to the surface of the grate where it was solidified by the relatively cool air passing through the grate and was fused into large masses. This again militated against uniformity of resistance and, consequently, of underfeeding since, as will be readily understood, the entire resistance over a considerable width of grate was destroyed when a large mass of fused ash was moved into the ash pit.

'Ihe aforesaid disadvantages have been avoided by providing an extension grate constructed in accordance with the present invention.

A convenient form of carrying out the present invention will hereinafter be described with reference to the accompanying drawings in which:

Fig. 1 is a longitudinal sectional view of our improved extension grate taken substantially along line' A-A of Fig. 3.

Fig. 2 is a sectional view taken substantially along line B--B of Fig. l, and

Fig. 3 is a sectional View taken substantially along line C--C of Fig. 1.

Referring to the accompanying drawings, the extension grate which is the subject of the present invention comprises a series of stationary bars i and movable bars 2, which, as shown in Figs. 2 and 3 are alternately arranged. The movable bars 2 are arranged in groups. In the drawings three bars are shown to each group but it will be understood that any convenient number of bars may be comprised in each group, the said groups extending acrossr the width of the Stoker.

Each of the bars forming a group are connected to each other by means of a shaft 3 as clearly shown in Fig. 3 at their free ends, the opposite ends of the said bars being pivotally mounted on a shaft 4. By dividing the bars into a series of groups each group can be independently adjusted with respect to the extent of its movement.

Arranged between each of the moving bars 2 is a y stationary bar I, one end of which is hooked onto the shaft 4 which connects the moving bars 2 and forms them into groups, the other end of which is removably secured by means of the forked portion 6 to a framework 'a' supporting refractory faced blocks 8 hereinafter to be referred to. By mounting the stationary bars l in this manner it will be seen that any bar can be easily removed for replacement whenv desired.

In order to operate the moving bars 2, the operating rod 9 of the extension grate is connected to one arm I0 of a bell-crank lever II suitably mounted on a plate I2, the other arm of the bell-crank lever being connected to a bfurcated link I3 secured to the shaft 3.

It will be seen that when the operating rod is operated the bell-crank lever II is turned, thus lifting the movable bars 2 through the link I3. By varying the stroke of the operating rod 9 in the known manner the amount of rise and fall of each group of moving -bars may be varied and as each group is provided with an independent operating rod, each group can be varied independently with respect to the next group of bars and all other groups of bars.

To assist in the formation of adequate resistance which will allow of uniform underfeeding of the fuel, the upper surface of the extension grate is arranged at a smaller angle to the horizontal than that of the extension grates hitherto in use, this being attained by raising the rearward end of the grate. The space thus formed between the lower or rear end of the extension grate and the top wall of the ash pit is built up by means of blocks 8, preferably having a refractory surface, secured to the framework I hereinbefore referred to. A further effect thus gained is the deepening of the ash pit which is in itself an advantage.

The principal advantages provided in the eX- tension grate hereinbefore described are: that it imparts an upward movement'l to the fuel and ash thereabove thereby preventing the formation of large masses of fused ash, that due to the prevention of large masses of fused ash, air is allowed a free passage through, and consumes the residual fuel immediately above the said grate and in addition, there is allowed the formation, together with the angle at which the upper surfare normally lies, of a resistance across the entire width of the stoker which is uniform irrespective of the change in the height of the ash in the ash pit, thereby facilitating the efficient underfeeding of the fuel down the tuyre section of the grate.

As a consequence of these improvements in operation, the fuel burning capacity of the Stoker is increased and smaller pieces of ash are fed to the ash pit than with the extension grates which were formerly in use. This feeding of smaller ash to the ash pit results Vin a more evenly packed pit and this greatly minimizes the risk of damage to that part of the lower portion of the grate surface which forms a Wall of the pit.

Having now particularly described and ascertained the nature of our said invention and in what manner the same is to be performed, We declare that what we claim is:

1. An extension grate for multiple retort, underfeed stokers comprising, a series of alternately disposed, stationary and moving bars arranged in side by side relation, means for connecting said moving bars into groups disposed in side by side relation, said means including a plurality of shafts, one for each of said groups, and independent means for actuating each of said groups of moving bars whereby an upward movement is imparted to the fuel and ash disposed thereabove.

2. An extension grate for multiple retort, underfeed stokers comprising, a series of alternately disposed, stationary and moving bars arranged in side by side relation, means for connecting said moving bars into groups disposed in side by side relation, said means including a plurality of shafts, one for each of said groups, and independent operating means for each of said groups whereby the extent of movement imparted to one group may be varied independently with respect to that imparted to the other groups across the width of the stoker.

3. An extension grate for multiple retort, underfeed stokers comprising, a series of alternately disposed, stationary and moving bars arranged in side by side relation, means for connecting said moving bars into groups disposed in side by side relation, said means including a plurality of shafts, one for each of said groups, and independent means for actuating each of said groups of moving bars whereby an upward movement is imparted to the fuel and ash disposed thereabove, each of said independent means including an operating rod, a bell crank lever operatively connected to said rod, and a link operatively connecting said bell crank lever to a group of said bars.

4. An extension grate for multiple retort, underfeed stokers comprising, a series of alternately disposed, stationary and moving bars arranged in side by side relation, means for connecting said moving bars into groups, said means including a plurality of shafts, one shaft being provided for each of said groups of moving bars, a plurality of axially aligned supporting shafts, means for removably securing one end of each of said stationary bars to a corresponding one of said supporting shafts, a framework disposed in spaced relation with said supporting shafts, a series of refractory blocks mounted in said framework, and means for removably securing the other end of each of said stationary bars to said framework in such a manner that said bars may be easily removed for replacement.

5. An extension grate for multiple retort underfeed stokers, comprising a series of alternately disposed stationary and moving bars arranged in side by side relation, means for connecting said moving bars into groups, said means including a plurality of shafts, one shaft being provided for each of said groups of moving bars, a plurality of axially aligned supporting shafts, means for removably securing one end of each of said stationary bars to a corresponding one of said supporting shafts, a framework, and hook means provided at the other end of each of said stationary bars for detachably securing the same to said framework.

THOMAS GEORGE WILLIAM WATSON. JOHN MCLEAN FERGUSON. 

